Modern techniques for constructing the walls of buildings may take numerous forms. Among these is the two-by-four (2×4) framed construction. Conventional 2×4 wall construction begins with framing of the walls with wood or metal (such as, steel) members. These wood or steel members typically have nominal dimensions of 2″×4″ and are, therefore, called “two-by-four” or 2×4. These 2×4s are oriented vertically and spaced at intervals generally either 16″ or 24″ and are each connected at the top and bottom to similar members that are horizontally oriented. This structure is referred to in the relevant art as a “framed” wall. A sheet of building wall substrate, such as plywood sheathing or other material, is then applied to the exterior of the framed wall.
A water-resistive barrier is then typically applied to the exterior of the sheathing, with an external wall cladding or finish then being applied directly over the water-resistive barrier. Many materials may be used for the external wall finish such as brick, stucco, Exterior Insulation and Finish System (EIFS), vinyl or aluminum siding, wood, etc. A sheet of gypsum board or drywall is typically applied to the interior facing surface of the framed wall toward the living area.
Exterior Insulation and Finish Systems (EIFS) are commonly used as an exterior wall cladding or finish on both commercial and residential buildings. EIFS are comprised of a rigid insulation board typically of expanded polystyrene (EPS) that is positioned directly over the exterior surface of a building wall substrate or over the exterior surface of the water resistive barrier which has been previously applied over a building wall substrate. A base coat layer is applied to the EPS insulation board. A reinforcing fiberglass mesh is substantially embedded in the base coat. A decorative and protective finish coat is applied over of the base coat and reinforcing fiberglass mesh.
During the installation of EIFS, an adhesive is applied to the back side of the rigid insulation board to adhere the insulation board to the water barrier which has been previously applied to the building wall sheathing. The adhesive material is often applied in a vertical ribbon pattern using a trowel having spaced apart notches. The insulation board is then brought into contact with the building wall sheathing such that the vertical ribbons of adhesive create channels that provide a drainage path to direct incidental moisture, if any, to the building exterior as well as attach the EIFS insulation board to the building wall sheathing. The remaining EIFS components (base coat, reinforcing mesh, finish coat) are applied in subsequent layers.
The effectiveness of EIFS to direct and drain incidental moisture can be impacted by the means used to install the adhesive and/or insulation. For example, if the vertical ribbons of adhesive are not applied properly or if the insulation board is not placed properly, the channels may not be capable of directing and draining moisture as intended.
If incidental water or moisture should penetrate the building envelope, the water barrier mentioned above serves as an additional obstacle to the intrusion of such water or other elements onto the sheathing material and into the wall. The water barrier also provides a surface to collect the moisture and direct it to the exterior of the building. If water is permitted to flow through the water resistive barrier and onto the sheathing material, the water may remain trapped in the sheathing material, which may result in deterioration of the sheathing material and underlying building components, thus requiring repair or replacement.
Moreover, moisture from the environment may become trapped between the external wall covering and the weather barrier. In the latter circumstance, if the weather barrier contains significant voids, cuts, gaps, etc., whether incurred during construction or due to settling of the structure, any such moisture may find its way through the opening in the weather barrier, onto the sheathing material, and eventually into the wall with the deleterious effects described above. Furthermore, such trapped moisture can reduce the wall system components' serviceability and service life.